Is this concept printable?

[Mr.H]

I have a Compact Veteran .25 with a plenum on it, so the airtube extends past the barrel shroud.

That limits what kind of moderator I can put on it, as it has to be the same diameter as the shroud, like this Hugget Belita

A couple of years ago, I had a friend who owns a CAD company, design and manufacture for me a few aluminum extensions, so I could use different diameter moderators instead of the Huggett (same diameter as the barrel shroud)

Here is what it looks like with the extension and a STO Pugio

I am not all that impressed with the STO unit. I think it’s too short, and regardless of what type of unit I put on here, I always get some sort of point of impact shift.

My question is to you moderator wizards, would it be possible to fabricate an all in one piece extension and moderator? I have read that some of your designs incorporate the tesla valve, I am wondering if a system like that might help my point of impact.

And fyi, I have tried multiple threaded shroud ends, not knowing, if possibly, there is a barrel alignment issue with the shroud ends. Regardless, if I use that aluminum extension or not, all the testing that I have done so far, gives me some sort of point of impact shift.

 

[bigHUN]

I don't know silencers, and I don't know your gun. My impression is that you would want to make that your shroud longer?
I have a 14mm OD barrel (FX Impact and L2) and looking for some shroud with internal air stripper.
These what I have ran into recently

Carbon Shroud Krale FX Impact

With this Krale Carbon Shroud for the FX Impact, you’ll give your FX Impact air rifle a fresh new look. The carbon offers a beautiful high-tech design and has as additional advantage that it’s lighter than the original barrel shroud. The 5.5

krale.shop

Shroud Huggett FX Wildcat 500 mm

This Huggett shroud for the FX Wildcat 500 mm replaces the original FX Wildcat 500 mm shroud and makes it significantly quieter. The shroud is made from light and strong aluminium and fits perfectly around the FX barrel by means of the included air stripper. Both production and assembly of the...

krale.shop

Posting just some examples maybe easier for you to get an idea.

 

[OldSpook]

I have a Compact Veteran .25 with a plenum on it, so the airtube extends past the barrel shroud.
View attachment 426502

My question is to you moderator wizards, would it be possible to fabricate an all in one piece extension and moderator? I have read that some of your designs incorporate the tesla valve, I am wondering if a system like that might help my point of impact.

That could be printed. Yes. If you can find someone to draw it. @subscriber you seeing this?

 

[Motorhead]

JMO ... anything printed is going to LACK the structural strength and ability to hold alignment with handling and temp changes etc ...

 

[OldSpook]

JMO ... anything printed is going to LACK the structural strength and ability to hold alignment with handling and temp changes etc ...

It's all about the design and the plastic/resin used.

 

[OldSpook]

I don't know silencers, and I don't know your gun. My impression is that you would want to make that your shroud longer?
I have a 14mm OD barrel (FX Impact and L2) and looking for some shroud with internal air stripper.
These what I have ran into recently

Carbon Shroud Krale FX Impact

With this Krale Carbon Shroud for the FX Impact, you’ll give your FX Impact air rifle a fresh new look. The carbon offers a beautiful high-tech design and has as additional advantage that it’s lighter than the original barrel shroud. The 5.5

krale.shop

Shroud Huggett FX Wildcat 500 mm

This Huggett shroud for the FX Wildcat 500 mm replaces the original FX Wildcat 500 mm shroud and makes it significantly quieter. The shroud is made from light and strong aluminium and fits perfectly around the FX barrel by means of the included air stripper. Both production and assembly of the...

krale.shop

Posting just some examples maybe easier for you to get an idea.

But I do think this idea is a better approach, even over something in metal... alignment when you hang a moderator on a shroud is more critical whether metal or plastic is used.

 

[subscriber]

Mr.H

You have provided a lot of information, but there is a lot of detail missing that might enable us to understand the cause of your POI shift problem.

If you need to adjust your POI up after attaching bits to the front of your airgun, is it possible that the added weight is causing some barrel droop? Or a change in harmonics. If the latter, the POI could shift in any direction, including up.

It would seem that some POI shift is typical when adding a moderator, providing it is not excessive. What is unacceptable would be if good grouping without a moderator opens up wildly after a moderator has been mounted. So, it might be useful to provide more detail about what is happening to your system.

It might be worth asking if the barrel is snug in the receiver, or if it can be made to move angularly when light force is applied. A little spring in the barrel and or shroud is typical for light airgun barrels, but I am talking about slop in the barrel retention that might be the root cause of your observed results. I would like to think that you have looked for such causes and eliminated them, but you know what they say about assuming anything.

A simple way to extend your shroud to be slightly ahead of the air tank is to undo the shroud's rear endcap clamping screw and slide the shroud forwards. It is free and can be restored if you don't like it. That said, the longer shrouds that bigHUN listed seem like attractive options. But, they won't fix a loose barrel socket, and cost a bundle.

I assume that the stock air diverter is screwed snugly to the barrel muzzle, and that its O-ring is snug in the shroud ID? If either of these are neglected, that alone could explain why hanging more bits from the shroud is making the system unhappy.

I am impressed with how many bits of custom hardware you have had made. The fact that this has not helped is perplexing, and might suggest there is something else the matter that is not being helped by the addition of precision hardware. If that is true, then adding a one piece shroud extension moderator combination is unlikely to help either. That is not to say that I am unwilling to design you a custom muffler to your specs.

It would recommend that you do some diagnostics, including the obvious, such as checking barrel mounting and centering at both ends. Angularity of the shroud faces and threads. It may be that if you flip the shroud end over end and use the more perpendicular face and thread, that there is an improvement with the hardware you have.

You can firmly apply a layer of masking tape to the front of your moderators, over the bore opening, then shoot a few shoots to see how well the system is aligned. Pellet holes near the edge of the moderator or shroud front cap bore indicate a problem, but not the cause. So testing with and without moderators should provide comparative data that you can think about, and should help with the diagnosis - even if it takes a few steps to get there.

If the masking tape shows pellet holes that are very far off center you may be seeing light clipping, that will not just shift your POI, it may blow groups. Depending on the type of moderator, offset pellet travel may aerodynamically steer the pellets to shift POI, or blow groups, if barrel harmonics or mounting slop are involved.

So, I would be happy to design something for you, but have a suspicion that a printed moderator is not going to solve your problem. To hedge my bets with what we know know, I would use extra generous projectile to baffle bore clearances. Just in case you are seeing a little clipping or projectile steering effects, regardless of their cause. Else, clipping with a printed moderator will damage it, and may result in a cascade failure with subsequent shots, as larger bits of plastic get in the way if the next pellet; and so on.

I hope this does not seem like a lot of words that say nothing. It is intended to help you confirm or dispute assumptions, and to gain clarity. Some of the assumptions include that your custom machined bits are as well made as the look. It may be insulting to your friend to check that, but it needs to be done. If the problem is present without adding custom bits, then the stock hardware is suspect. Adding even good extensions may make misalignment of the moderator worse, it the stock hardware has an angularity problem.

This is probably about as far as I should go, without more information; and hardware confirmation.

 

[Mr.H]

Thanks for the replies everyone. Let me take some more pictures tomorrow when the light is better and show you all the anchor points and other measurements

 

[FelixS]

How about having your friend machine a combination extention/end cap that would replace the rear cap on your moderator?

 

[delooper]

Yes, you can make an all in one unit. Moderators don't have to be cylindrical -- take a look at the Edgun Leshiy 2's stock moderator.

It's just a question of what shape you want (that will fit) and taking the time to design it properly.

 

[Mr.H]

I don't know silencers, and I don't know your gun. My impression is that you would want to make that your shroud longer?
I have a 14mm OD barrel (FX Impact and L2) and looking for some shroud with internal air stripper.
These what I have ran into recently

Carbon Shroud Krale FX Impact

With this Krale Carbon Shroud for the FX Impact, you’ll give your FX Impact air rifle a fresh new look. The carbon offers a beautiful high-tech design and has as additional advantage that it’s lighter than the original barrel shroud. The 5.5

krale.shop

Shroud Huggett FX Wildcat 500 mm

This Huggett shroud for the FX Wildcat 500 mm replaces the original FX Wildcat 500 mm shroud and makes it significantly quieter. The shroud is made from light and strong aluminium and fits perfectly around the FX barrel by means of the included air stripper. Both production and assembly of the...

krale.shop

Posting just some examples maybe easier for you to get an idea.

I agree with you 100%. When I first got this gun in about two years ago, and after I discovered that the gun was honestly too loud for my ear, I asked on this forum, if anybody knew anybody that could make a custom shroud. And I got no takers and of course I inquired with the dealers in the United States about the possibility of ordering a standard length barrel and shroud, which is 4 inches longer than the barrel that I have on my gun right now, but I couldn’t find any locally, or with the manufacturer. And now that this gun isn’t being produced anymore, I am either going to have to shoot it as is, or find another way, in which I could tame the bark of this gun.

As for Mr. subscriber, I am going to start posting some drawings and photographs of the gun and shroud. This is a photo of the factory shroud removed, with the baffle stack extracted from the shroud tube. There are three anchor points for the barrel, one back at the receiver, and then two that holds the Picatinny rail system. The end of the barrel extends approximately 2 7/8 of an inch past that last anchor point the threads on the barrel are the standard 1/2 x 20 UNF.

Here are some of the details of the shroud. The overall length on the shroud body is approximately 6 7/8 of an inch. The diameter is 1.22 inches. The end of the shroud that sleeves into the barrel starts off with a inserted Delrin sleeve, where 1/2 inch of that sleeve makes contact with the barrel diameter. Approximately 2 1/8 of an inch into the shroud, the manufacturerinserted a retaining clip. On the front side of that retaining clip, there is a threaded and ported anchor, threaded 1/2 x 20 UNFthen comes the baffle stack.

The assembled weight of the factory moderator is 5.08 ounces. That extension that I had my friend design and fabricate plus the weight of that STO moderator comes in at about 6.0 ounces, and I think that’s where the problem is. That extra weight isn’t making the barrel droop but the extra weight on the end of the moderator is causing the shroud to fall down a little bit, which is giving me my of Poi shift. The exit hole on the STO moderator is for a .30, so I dont get clipping. But on that Huggett moderator, that was initially made for .25. And that clipped, so I had that bored out to .30.

Here is another photograph of that Huggett directly threaded on to the end of the barrel, without the factory shroud installed. It honestly is louder than the factory shroud, as it only 4 3/4”. And the Huggett isn’t really a cone type baffle, it’s more or less like an airstripper with a screen and felt.

Maybe before I get too far in front of myself, I should ask, number one if any of you guys that have fabricated moderators, if you think the original shroud design could be printed longer to accommodate another cone and spacer? (The original shroud is made out of aluminum, obviously.). And can the factor baffle, spacers and cones be printed rather than using a stock aluminum ones?

Or, what about the possibility of leaving the factory shroud off, and fabricating a new moderator that will screw right on to the end of the barrel, that is approximately six or 7 inches long rather than 4 1/2”?? The diameter would have to be 1.22 “ so it would fit over the air tube.

Don’t most of you fabricators prefer a wider diameter moderator for optimum sound dampening? Do you think a longer unit would work for me or not?

I think this is a good stopping point for me right now, I’ll wait for some more replies from everybody watching this thread. Thank you very much for following along.

 

[Motorhead]

I made this up a couple years ago to EXTEND the muzzle exit slightly.
It threaded onto an LDC 1/2-20 adapter.

It's diameter could have been equal to shroud, but was a tad larger in this one.
An empty can with a single layer of closed loop patio carpet lining it.

Not only did it extend exit it had a very favorable effect on noise being very low when in place.

 

[Airgunmann]

I think a koi is about 6 to seven inches and is right around the same size if I remember correctly. The other thing would be to install a longer Barrel and make a longer shroud some airguns it's not so bad others it's a pain

 

[OldSpook]

@Mr.H That Huggette is just about perfect for a 40 fpe 22...
Seriously though, if you are wanting a moderator the same diameter as the shroud, you should hit EBay and order the CF tubing you need to simply replace the shroud you have. For $30.00 or so you can order a 500mm length of CF that is 30mm x 28mm or 32mm x 30mm. Either or both of those would probably work in your application AND you already have all the hardware you'd need to put the thing together. At that point all you would be looking for would be the insert AND you'd still have a threaded muzzle on the shroud. If you needed O-rings to space the tube off the barrel someone could print them using TPU.

 

[subscriber]

Thank you Mr.H,

You have corrected my mental model. Because the overall package is so similar to the Bullshark, I had imagined that the shroud guts would be similar. They are not.

The barrel should be very stiff based on the number of capture points and very short frontal projection. But as you pointed out, that short barrel projection makes for poor angular support of the shroud.

There is nothing inherently wrong with the stock approach, except that clearance between the parts will tend to cause a large angular misalignment. As you noted, the more weight you add to the end, the more the shroud would droop.

It is hard for me to tell how much clearance there is between the shroud and the air tank, but it looks so close that they may make contact near the front end dynamically on the shot. That is likely to cause the shroud to bounce, and likely change the effective barrel harmonics in a bad way. If there is any variation in that contact due to gravity from the angle of the shot; or how how you hold the airgun, there is likely a shift in the shroud to airtank interaction.

I suspect that a slightly larger shroud to airtank clearance would help. If that is not practical, then a shroud to airtank support, or "barrel band" might prevent shroud droop and improve consistency of shroud and barrel harmonics.

All that said, there are a number of approaches that can be tried along the lines you mentioned. This includes replacing all the shroud parts that attach to the barrel, and combining them into one part. That makes the unit self aligned, but it may still benefit from a forward support that attaches to the air tank - assuming this air tank is filled on the gun, and not replaceable like that of the HW100.

As they say, the devil is in the details. If the stock shroud ID and OD don't leave much clearance with the barrel OD, then replacing that with a much thicker plastic walled tube would make the reflex space meaningless. So, it might make sense to keep the shroud tube, and just make the plastic insert that screws directly onto the barrel stud a snug fit into the shroud tube.

What is the stock shroud ID measurement? Measure around the tube in a few places because the tube my not be perfectly round.

What is the distance from the barrel support rail end to the front of the air tube? How much would you like the the front of the moderator to project ahead of the air tube? Some of the dimensions you have given may infer some of the ones I am asking for. The most important dimension for sound suppression is length ahead of the barrel muzzle. If you could make that 8" that should be enough to work with.

If you want or will allow the moderator to project perhaps 4" ahead of the air tube end, the OD of that frontal section could be larger than the section behind the front of the air tube - if required. The 1.22" stock shroud OD is not very large.

What OldSpook suggested should result in a more elegant solution. It would save some weight over he aluminum shroud tube, although that can't be very much for such a short tube.

If one is going to reuse some or most of the stock hardware, then some effort should be made to improve the alignment of the parts to the shroud tube - stock or CF replacement. One way to take slop out without making assembly difficult is to cut O-ring grooves around all the metal parts that fit into the shroud tube - assuming the wall thickness of the parts supports that. Unless the aluminum hardware is already a sliding fit in the shroud tube, it may be possible to wind some thin tape around the parts until they will just go into the tube. What O-ring fit improvers are good for, is to allow the assembly to find a low stress position, so the various bits in the tube don't fight each other.

That said, if one is reusing the stock shroud tube and coupling that with a custom insert/moderator, then the rear shroud support and might be the only part that might need its fit improved inside the shroud.

Or, as the front of the shroud ID is threaded, the custom insert could be threaded to the shroud (first), and to the barrel muzzle. The rear of the shroud could be blanked off with a custom plug that simply buts against the barrel support, as the shroud would then already be constrained at two places. The stock delrin barrel to shroud support might work for that.

The bottom line is that the stock section of baffles 4 7/16" is way to short to make this PCP quiet. Doubling that length should give it a fighting chance. So, the question is, how long would you like a single custom insert to be from the muzzle stud shoulder? This assumes that it replaces the need for removable moderators.

What is the barrel OD, and 1/2-20 stud length? I have buried the other required dimensions in the text above. If you write them down as you read through is a problem, I can come back and make a short list.

The front shroud thread designation can be measured off the male threaded parts you have on hand. OD and pitch?

While I am thinking about this, what is the air tube diameter? What is the barrel OD to air tube clearance of barrel to air tube center to center spacing? With the above, I can do a layout to see what fits in and how it may look, compared to what you want or can tolerate. Speaking of tolerate; how large a moderator OD can you tolerate ahead of the air tube?

When I have the missing dimensions I will be able to distill my own mental meanderings above into a more coherent plan. It need to be simple. It needs to work well, rather than have a lot of impressive features.

 

[subscriber]

More detail, please: What is the Compact Veteran's overall barrel length, and what power level are you shooting at?

 

[subscriber]

Mr.H,

I have taken the dimensions given to do a quick layout. What I don't know I have assumed:
Barrel OD: 15 mm
Barrel threaded stud length: 10 mm
Shroud tube ID: 29 mm (non threaded diameter)
Air tank OD: 31 mm
Barrel to air tank center distance: 33 mm (2 mm space between shroud tube and air tank)
Total air tank length from barrel support rail forward face: 222 mm

Stock Baffle OD?
Stock air diverter OD (part the screws onto barrel stud and lets air into rear of shroud) ?

Please refine these dimensions, so I can design a shroud extension muffler that will fit.

 

[subscriber]

So, using the above layout to add a potential shroud extension moderator is simple enough. The first image below adds a 50 mm OD snout just over 4" longer than the front of the air tank (assumed air tank length stated above). That equates to a total part length ahead of the barrel muzzle of 10"; assuming we can print a part 264 mm long, including the barrel stud length.

The second image shows an 8" insert length ahead of the barrel muzzle, with a "nose length" of just over 2" ahead of the air tank. The nose OD is reduced to 40 mm, or a bit over 1.5". I would not like to go under this to meet your performance expectations.

The third image is the same as the second, except the nose OD is 50 mm.
In all three versions, the shroud OD extension is just over 2".

The fourth image is the same as the first, except the nose OD is at a nominal 2". That is probably at a good practical limit. It provides room for what I have in mind, without being silly:

The fifth images is the same as the first and fourth, except the nose OD is reduced to 45 mm:

Of course, you could have a longer insert, but there are not many printers that can produce such tall parts. The part need to be printed vertically, standing on its front face to produce the internal baffles and threads (not shown).

You might prefer the appearance of a different OD nose section; or nose OD to length proportion. If so, please advise. My nose OD preference, based on appearance and usable space would be 45 to 50 mm, with the total insert length as long as is practical to print (around 10"). 8" is definitely possible, and so is 9" with the printer I have in mind - I should check that with my printer guy.

 

[subscriber]

I just realized a small error in representing my intent: The shroud extension would have the same OD as the stock shroud tube OD, up to the insert's larger OD "nose" section. See image below with red arrows showing the small step from shroud ID to OD:

EDIT: My printer guy can do a max of 250 mm tall, so that is what I will use in a real design.

 

[Mr.H]

Thank you Mr.H,

You have corrected my mental model. Because the overall package is so similar to the Bullshark, I had imagined that the shroud guts would be similar. They are not.

The barrel should be very stiff based on the number of capture points and very short frontal projection. But as you pointed out, that short barrel projection makes for poor angular support of the shroud.

There is nothing inherently wrong with the stock approach, except that clearance between the parts will tend to cause a large angular misalignment. As you noted, the more weight you add to the end, the more the shroud would droop.

It is hard for me to tell how much clearance there is between the shroud and the air tank, but it looks so close that they may make contact near the front end dynamically on the shot. That is likely to cause the shroud to bounce, and likely change the effective barrel harmonics in a bad way. If there is any variation in that contact due to gravity from the angle of the shot; or how how you hold the airgun, there is likely a shift in the shroud to airtank interaction.

I suspect that a slightly larger shroud to airtank clearance would help. If that is not practical, then a shroud to airtank support, or "barrel band" might prevent shroud droop and improve consistency of shroud and barrel harmonics.

All that said, there are a number of approaches that can be tried along the lines you mentioned. This includes replacing all the shroud parts that attach to the barrel, and combining them into one part. That makes the unit self aligned, but it may still benefit from a forward support that attaches to the air tank - assuming this air tank is filled on the gun, and not replaceable like that of the HW100.

As they say, the devil is in the details. If the stock shroud ID and OD don't leave much clearance with the barrel OD, then replacing that with a much thicker plastic walled tube would make the reflex space meaningless. So, it might make sense to keep the shroud tube, and just make the plastic insert that screws directly onto the barrel stud a snug fit into the shroud tube.

What is the stock shroud ID measurement? Measure around the tube in a few places because the tube my not be perfectly round.

What is the distance from the barrel support rail end to the front of the air tube? How much would you like the the front of the moderator to project ahead of the air tube? Some of the dimensions you have given may infer some of the ones I am asking for. The most important dimension for sound suppression is length ahead of the barrel muzzle. If you could make that 8" that should be enough to work with.

If you want or will allow the moderator to project perhaps 4" ahead of the air tube end, the OD of that frontal section could be larger than the section behind the front of the air tube - if required. The 1.22" stock shroud OD is not very large.

What OldSpook suggested should result in a more elegant solution. It would save some weight over he aluminum shroud tube, although that can't be very much for such a short tube.

If one is going to reuse some or most of the stock hardware, then some effort should be made to improve the alignment of the parts to the shroud tube - stock or CF replacement. One way to take slop out without making assembly difficult is to cut O-ring grooves around all the metal parts that fit into the shroud tube - assuming the wall thickness of the parts supports that. Unless the aluminum hardware is already a sliding fit in the shroud tube, it may be possible to wind some thin tape around the parts until they will just go into the tube. What O-ring fit improvers are good for, is to allow the assembly to find a low stress position, so the various bits in the tube don't fight each other.

That said, if one is reusing the stock shroud tube and coupling that with a custom insert/moderator, then the rear shroud support and might be the only part that might need its fit improved inside the shroud.

Or, as the front of the shroud ID is threaded, the custom insert could be threaded to the shroud (first), and to the barrel muzzle. The rear of the shroud could be blanked off with a custom plug that simply buts against the barrel support, as the shroud would then already be constrained at two places. The stock delrin barrel to shroud support might work for that.

The bottom line is that the stock section of baffles 4 7/16" is way to short to make this PCP quiet. Doubling that length should give it a fighting chance. So, the question is, how long would you like a single custom insert to be from the muzzle stud shoulder? This assumes that it replaces the need for removable moderators.

What is the barrel OD, and 1/2-20 stud length? I have buried the other required dimensions in the text above. If you write them down as you read through is a problem, I can come back and make a short list.

The front shroud thread designation can be measured off the male threaded parts you have on hand. OD and pitch?

While I am thinking about this, what is the air tube diameter? What is the barrel OD to air tube clearance of barrel to air tube center to center spacing? With the above, I can do a layout to see what fits in and how it may look, compared to what you want or can tolerate. Speaking of tolerate; how large a moderator OD can you tolerate ahead of the air tube?

When I have the missing dimensions I will be able to distill my own mental meanderings above into a more coherent plan. It need to be simple. It needs to work well, rather than have a lot of impressive features.

It's going to take me some time to catch up to your posts and questions. I'm working on a cup of Joe, I'll be in touch when my brain kicks in